In a multiuser multi-input multi-output (hereinafter, MIMO) wireless communications system, a base station using a multi-transmission antenna spatial multiplexes and transmits data of each user based on channel information between the base station and a plurality of users, thereby providing a high cell capacity under limited frequency and power resources. Such multiuser-MIMO wireless communication system calculates a beam-forming vector of coordinated beam-forming method when transmitting a signal to a plurality of users, and then, by using this calculated beam-forming vector, transmits a transmission signal optimized for a plurality of users respectively. The process of obtaining a beam-forming vector for typical coordinated beam-forming is performed by a repetitive calculation algorithm, so that it is usually very difficult to accurately measure the number of times of repetitive calculation until it converges into an optimized beam-forming vector. Thus, in the data transmission on the wireless telecommunications system, a delay may occur until the beam-forming vector calculation is converged, such that system instability can be caused. Accordingly, if the number of times of the repetitive calculation is compulsorily limited, the performance of the coordinated beam-forming is reduced due to the imprecision of the beam-forming vector. Moreover, in the repetitive calculation procedure, a complicated matrix operation like Singular Value Decomposition (SVD) should be repeatedly executed.